"Your infant may not be able to tell you that you seem stressed or ask you what is wrong, but our work shows that, as soon as she is in your arms, she is picking up on the bodily responses accompanying your emotional state and immediately begins to feel in her own body your own negative emotion," study researcher Sara Waters, of New York University, said in a statement. Waters worked with researchers at the University of California, San Francisco, on the Psychological Science study.

For the study, researchers examined emotion and heart rate in babies whose mothers were put through a stressful task. The study included 69 mothers and their 12- to 14-month-old babies, all of whom had cardiovascular sensors attached to them to record heart rate.

The researchers separated the mothers and babies so that the mothers could give a five-minute speech and go through a five-minute Q & A session. Evaluators were assigned to review each mother's speech and Q & A session, giving either positive, negative or no feedback. The mothers who received the negative feedback had more negative emotions and fewer positive emotions, as well as increased cardiac stress, after undergoing this experience.

Then, the researchers reunited the mothers with their babies. Within minutes of going back to their mothers, the babies seemed to "track" their mother's stress response, in the effort of an increased heart rate. And the greater the other's stress response, the greater the baby's response seemed to be.

While more research is needed to tease out how the babies are able to track their mothers' emotions, they noted that it could be through smell, vocal tension or even facial expressions.

CORRECTION: A previous version of this article incorrectly stated the first name of the researcher. Her name is Sara Waters.